1. Field of the Invention
The present invention relates to a light emitting device with a control system for light emission of a light emitting element and to an element substrate including the control system.
2. Description of the Related Art
In display panels using an organic electroluminescence medium, a flat panel formed of pixels using thin film transistors has been disclosed (e.g. Patent Document 1). A configuration and an operation of a pixel included in such a conventionally well known flat panel are described in brief hereinafter with reference to drawings.
A pixel shown in FIG. 7 comprises a switching transistor 700 whose gate is connected to a scan line 705, either a source or a drain of which is connected to a signal line 704 and the other is connected to a gate of a driving transistor 701. A source of the driving transistor 701 is connected to a power supply line 706 and a drain thereof is connected to an anode of a light emitting element 703. The other terminal of the light emitting element 703 is connected to a counter electrode 707. A capacitor 702 is disposed so as to hold a potential difference between the gate and the source of the driving transistor 701. A predetermined voltage is applied from a power supply to the power supply line 706 and the counter electrode 707 so as to have a potential difference therebetween.
When the switching transistor 700 is turned ON by a signal of the scan line 705, a video signal of the signal line 704 is input to the gate of the driving transistor 701. A potential difference between the input video signal and the power supply line 706 is a voltage Vgs between the gate and the source of the driving transistor 701. Then, a current is supplied to the light emitting element 703 and thereby the light emitting element 703 emits light.
Patent Document 1:
Japanese Patent Application Laid-Open No. Hei 8-234683, pp. 5, FIG. 1